Investigators have found concrete evidence on computers used by Pfc. Bradley Manning that link him with the leak of classified Afghanistan war reports, a U.S. defense official said.

The disclosure came as Defense Secretary Robert Gates pledged Thursday to "aggressively investigate the leak" and find ways to prevent further breaches, and told reporters that he had invited the Federal Bureau of Investigation to assist the probe.

Defense officials said the FBI was investigating whether civilians aided Pfc. Manning in providing the information to WikiLeaks, a Web-based group that this week released 76,000 secret reports from Afghanistan.

Pfc. Manning already was charged by the military in July with illegally taking secret State Department files and disseminating a classified video, which defense officials said was the one released by WikiLeaks showing a U.S. military helicopter firing on a group of people in Baghdad. Two Reuters journalists and seven others were killed in the 2007 incident.
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PM Report: Gates Says Leaks May Cause Huge Damage
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Defense Secretary Robert Gates said the Afghan leaks could cause extensive damage to the allied mission. Meanwhile, investigators have found evidence linking Pfc. Bradley Manning to the leaks, according to a defense official. Julian Barnes discusses. Also, Aaron Zitner discusses developments in the probe of Rep. Charles Rangel.

Friends and acquaintances of Pfc. Manning's in Oklahoma said they were interviewed by Army and State Department investigators last month, who asked whether they had received email or packages from Pfc. Manning.

The 22-year-old private worked in intelligence operations in Baghdad. He was supposed to be examining intelligence relevant to Iraq, but defense officials said Pfc. Manning used his "Top Secret/SCI" clearance to tap into documents around the world.

Regardless of his personal or political beliefs, he betrayed a trust which placed U.S. or allied troops at increased risk.

In the process of obtaining elevated levels of clearance he was clearly informed of the consequences of betraying that access, so he made a fully informed decision.

This isn't about politics or freedom of speech - it's about an informed individual making a conscious choice to release classified information - during wartime no less. The UCMJ is clear on the subject.

Not that uncommon at all. Basically everybody who works in intel and a multitude of other jobs in the military get TS/SCI clearances before they are even to their school for MOS/Rate training as some of the schools require that you have the clearance to even work on some of the machinery and computer systems that they train on.